s = "3412830957ljl@qqlshadhalj.com"
if("@" not in s or "." not in s ):
    print("错误")
else:
    print("前提条件满足")
    l1=s.index("@")
    s1=s[0:l1]
    s2=s[l1+1::]
    l2=s2.index(".")
    s3=s2[0:l2]
    s4=s2[l2+1::]
    L1=len(s1)
    L2=len(s3)
    if((L1<2 or L1>15) or (L2<1 or L2>8)):
        print("长度错误")
    else:
        print("长度条件满足")

        m=0
        n=0

        for i in s1:#判断s1
            m=m+1
            if(i>="a" and i <="z") or(i>="0" and i<="9"):
                pass
            else:
                break
        for j in s3:#判断s3
            n=n+1
            if(j>="a" and j <="z") or(j>="0" and j<="9"):
                pass
            else:
                break

        if(m!=L1 or n!=L2):
            print("内容不正确")
        else:
            print("正确")





